In his early teens, he spent some time with the Bedouin in the Arabian desert.[8] Following in the footsteps of his father, Philby continued to Westminster School, which he left in 1928 at the age of 16.[7] He won a scholarship to Trinity College, Cambridge, where he studied history and economics. He graduated in 1933 with a 2:1 degree in Economics.[9]
I'm bet that he found the Bedouin to be much better people that those he met at posh schools. Also reading the Wikipedia article, it seems close to certain that he intended to be a Soviet spy from early on.